1. Field of the Invention
The present invention is generally related to an exhaust treatment device for an internal combustion engine and, more particularly, to an exhaust treatment device for use in conjunction with an engine of a marine propulsion system in Which inner and outer chambers of the device are configured to advantageously direct a stream of exhaust gases through a high temperature region to oxidize certain elements within the exhaust stream.
2. Description of the Prior Art
Various types of exhaust treatment devices are known to those skilled in the art. Some exhaust treatment devices incorporate catalysts which advantageously affect the constituents of an exhaust stream while others provide a thermal reactor without the additional use of a catalyst bed.
U.S. Pat. No. 3,911,676, which issued to Jensen on Oct. 14, 1975, describes an exhaust system which comprises a two stage exhaust manifold reactor adapted to lower the nitrogen oxide, hydrocarbon and carbon monoxide content of exhaust gas of internal combustion engines. The first stage comprises a catalytic reactor housing connected proximate to the engine exhaust ports and containing a catalyst bed between spaced perforate retainers such that the host exhaust gas passes through the catalyst bed whereby nitrogen oxides are chemically reduced. Air is injected into the exhaust gas after traversing the catalyst bed. Air injection can be accomplished by one or more injection tubes having a plurality of openings in its side wall. Connected proximate to the catalytic reactor housing is a non-catalytic thermal oxidation reactor which receives the hot exhaust gas/air mixture and wherein hydrocarbon and carbon monoxide are oxidized.
U.S. Pat. No. 3,902,853, which issued to Marsee et al on Sep. 2, 1975, describes an exhaust converter for an internal combustion engine which comprises an outer housing rigidly connected directly to the exhaust outlets of the engine and a light weight flexibly constructed inner housing suspended inside the rigid outer housing. The inner housing contains a flexibly suspended catalyst container dividing it into an inlet plenum and a thermal non-catalytic reactor compartment. Air injection means are provided in the thermal reactor. The catalytic stage reduces nitrogen oxides and the thermal reactor oxidizes hydrocarbon and carbon monoxide. The light flexible construction of the inner housing allows it to expand and contract in response to thermal shock without destroying itself.
U.S. Pat. No. 3,826,089, which issued to Nakajima et al on Jul. 30, 1974, describes an air pollution preventive arrangement. The arrangement is intended for use with an internal combustion engine for motor vehicles, adapted to reduce the concentrations of noxious compounds such as unburned hydrocarbons and carbon monoxides contained in the engine exhaust gases. The arrangement comprises a thermal reactor for primarily recombusting the exhaust gases and a catalytic converter for secondarily recombusting the exhaust gases passed from the thermal reactor so as to oxidize the residual unburned compounds. An air injection unit supplies additional air which is mixed, in a limited proportion, to the exhaust gases entering the thermal reactor to aid in the primary recombustion of the exhaust gases therein. The noxious unconsumed hydrocarbons and carbon monoxides are thus converted into innocuous compounds at efficiencies which are far higher that those attained where the thermal reactor or the catalytic converter is employed independently.
U.S. Pat. No. 3,947,545, which issued to Ishida et al on Mar. 30, 1976, describes a purification system for exhaust gas. There are provided in the patent an improved thermal reactor apparatus for, an improved method of, purifying exhaust gases, particularly from a motor vehicle, wherein thermal oxidation and catalytic oxidation of the carbon monoxide and hydrocarbon contents of the exhaust gases and/or catalytic reduction of the nitrous oxide contents of the exhaust gases are effected within an environment such that at least some of the components of the reactor exposed to the exhaust gases are coated with and/or made of a catalytic alloy capable of acting as a catalyst for oxidation of the carbon monoxide and hydrocarbon contents of the exhaust gases and for reduction of the nitrous oxide contents of the exhaust gases.
U.S. Pat. No. 3,934,412, which issued to Masaki et al on Jan. 27, 1976, describes a thermal reactor for afterburning automotive internal combustion engine exhaust gases. Reaction heat generated by oxidation in presence of an oxidation catalyst maintains a sufficient afterburning temperature during low engine load operation.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Many different types of reactors and catalyst systems are well known to those skilled in the art. These devices are used to reduce the amount of noxious elements in the exhaust stream of an internal combustion engine. Many different types of outboard motors and other marine propulsion systems are known to those skilled in the art.
Internal combustion engines used in conjunction with marine propulsion systems are cooled by drawing water from a body of water in which the marine propulsion system is operated, circulating that water in thermal communication either directly with the internal combustion engine or with a closed loop cooling system of the internal combustion engine, and then returning the water to the body of water from which it was drawn.
It would be beneficial if an internal combustion engine of a marine propulsion system could be provided with a reactor or catalyst device that is cooled by the normal cooling system of the engine and operated in such a way that internal temperatures of the reactor are maintained at a sufficiently high magnitude to promote oxidation and therefore efficiently decrease the amount of noxious components within the exhaust stream of the internal combustion engine. It would further be beneficial if such a device were constructed in a way that allows components having extremely different temperatures to be supported in such a way so as to reduce damage that might otherwise occur because of the expansions caused by extreme temperature differentials between components that are proximate to each other.
An exhaust treatment device for an internal combustion engine of a marine propulsion system, made in accordance with the present invention, comprises an outer chamber and a first inner chamber contained within the outer chamber and nonrigidly supported by the outer chamber through the use of sliding members. A first exhaust inlet conduit is disposed in fluid communication with the first inner chamber for directing a flow of exhaust gases into the first inner chamber from a location external to the exhaust treatment device. As a result of this structure, the first inner chamber can move relative to the outer chamber in response to changes in the temperature difference between the first inner chamber and the outer chamber.
A preferred embodiment of the present invention further comprises an outer support rail attached to the outer chamber and a first inner support rail attached to the first inner chamber and shaped to be received by the outer support rail. The outer support rail and first inner support rail are configured to cooperate with each other to slidably support the first inner chamber relative to the outer chamber. A first plurality of transfer passages is formed as part of the exhaust treatment device to provide fluid communication between the first inner chamber and the outer chamber.
A liquid cooled housing is attached to the internal combustion engine and the outer chamber is disposed within a cavity of the liquid cooled housing. A first end of the first inner chamber is disposed at a first end of the exhaust treatment device and a second end of the first inner chamber is disposed at a second end of the exhaust treatment device. The outer chamber is disposed in fluid communication with an exhaust conduit of the engine at the first end of the exhaust treatment device. The first plurality of transfer passages are formed in the wall of the first inner chamber at a location which is closer to the second end of the exhaust treatment device than to the first end of the exhaust treatment device.
A particularly preferred embodiment of the present invention further comprises a second inner chamber contained within the outer chamber and a second inner support rail attached to the second inner chamber and shaped to be received by the outer support rail. The outer support rail and the second inner support rail are configured to cooperate with each other to slidably support the second inner chamber relative to the outer chamber. A second plurality of transfer passages is formed as part of the exhaust treatment device to provide fluid communication between the second inner chamber and the outer chamber. Also, a second exhaust inlet conduit is disposed in fluid communication with the second inner chamber for directing a flow of exhaust gases into the second inner chamber. A first end of the second inner chamber is disposed at the first end of the exhaust treatment device and a second end of the second inner chamber is disposed at the second end of the exhaust treatment device. The second plurality of transfer passages are formed in a wall of the second inner chamber at a location which is closer to the second end of the exhaust treatment device than to the first end of the exhaust treatment device.
Certain embodiments of the present invention can further comprise a catalyst disposed within the first and second inner chambers.